Probing particle physics and astrophysics with extragalactic cosmic-rays, gamma-rays and neutrinos

The highest energy cosmic rays observed posses macroscopic energies and the ir origin is likely to be associated with the most energetic processes in t he Universe. Their existence triggered a flurry of theoretical explanations ranging from conventional shock acceleration to particle physics beyond th e Standard Model and processes taking place at the earliest moments of our Universe. Furthermore, many new experimental activities promise a strong in crease of statistics at the highest energies and a combination with gamma-r ay and neutrino astrophysics will put strong constraints on these theoretic al models. Detailed Monte Carlo simulations indicate that charged ultra-hig h energy cosmic rays can also be used as probes of large scale magnetic fie lds whose origin may open another window into the very early Universe. We g ive an overview over this quickly evolving research field.